Implement balance table

ipld/hamt/src/hamt.rs

@@ -156,7 +156,7 @@ where
         V: DeserializeOwned,
     {
         match self.root.get(k, self.store, self.bit_width)? {
-            Some(v) => Ok(Some(from_ipld(v).map_err(Error::Encoding)?)),
+            Some(v) => Ok(Some(from_ipld(&v).map_err(Error::Encoding)?)),
             None => Ok(None),
         }
     }
@@ -201,4 +201,35 @@ where
     pub fn is_empty(&self) -> bool {
         self.root.is_empty()
     }
+
+    /// Iterates over each KV in the Hamt and runs a function on the values.
+    ///
+    /// This function will constrain all values to be of the same type
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use ipld_hamt::Hamt;
+    ///
+    /// let store = db::MemoryDB::default();
+    ///
+    /// let mut map: Hamt<usize, _> = Hamt::new(&store);
+    /// map.set(1, 1).unwrap();
+    /// map.set(4, 2).unwrap();
+    ///
+    /// let mut total = 0;
+    /// map.for_each(&mut |_, v: u64| {
+    ///    total += v;
+    ///    Ok(())
+    /// }).unwrap();
+    /// assert_eq!(total, 3);
+    /// ```
+    #[inline]
+    pub fn for_each<F, V>(&self, f: &mut F) -> Result<(), String>
+    where
+        V: DeserializeOwned,
+        F: FnMut(&K, V) -> Result<(), String>,
+    {
+        self.root.for_each(self.store, f)
+    }
 }

ipld/hamt/src/node.rs

@@ -6,11 +6,10 @@ use super::hash_bits::HashBits;
 use super::pointer::Pointer;
 use super::{Error, Hash, HashedKey, KeyValuePair, MAX_ARRAY_WIDTH};
 use cid::multihash::Blake2b256;
-use forest_encoding::{de::Deserializer, ser::Serializer};
-use forest_ipld::Ipld;
+use forest_ipld::{from_ipld, Ipld};
 use ipld_blockstore::BlockStore;
 use serde::de::DeserializeOwned;
-use serde::{Deserialize, Serialize};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use std::borrow::Borrow;
 use std::fmt::Debug;
 
@@ -129,6 +128,29 @@ where
         self.pointers.is_empty()
     }
 
+    pub(crate) fn for_each<V, S, F>(&self, store: &S, f: &mut F) -> Result<(), String>
+    where
+        V: DeserializeOwned,
+        F: FnMut(&K, V) -> Result<(), String>,
+        S: BlockStore,
+    {
+        for p in &self.pointers {
+            match p {
+                Pointer::Link(cid) => match store.get::<Node<K>>(cid)? {
+                    Some(node) => node.for_each(store, f)?,
+                    None => return Err(format!("Node with cid {} not found", cid)),
+                },
+                Pointer::Cache(n) => n.for_each(store, f)?,
+                Pointer::Values(kvs) => {
+                    for kv in kvs {
+                        f(kv.0.borrow(), from_ipld(&kv.1).map_err(Error::Encoding)?)?;
+                    }
+                }
+            }
+        }
+        Ok(())
+    }
+
     /// Search for a key.
     fn search<Q: ?Sized, S: BlockStore>(
         &self,

ipld/src/lib.rs

@@ -40,11 +40,11 @@ where
 
 /// Convert a `Ipld` structure into a type `T`
 /// Currently converts using a byte buffer with serde_cbor
-pub fn from_ipld<T>(value: Ipld) -> Result<T, String>
+pub fn from_ipld<T>(value: &Ipld) -> Result<T, String>
 where
     T: DeserializeOwned,
 {
     // TODO find a way to convert without going through byte buffer
-    let buf = to_vec(&value).map_err(|e| e.to_string())?;
+    let buf = to_vec(value).map_err(|e| e.to_string())?;
     from_slice(buf.as_slice()).map_err(|e| e.to_string())
 }

node/clock/src/lib.rs

@@ -79,6 +79,7 @@ impl ChainEpochClock {
     }
 }
 
+// TODO revisit usage of the Sub impls, these will panic (checked sub or floored sub would be safer)
 impl Sub for ChainEpoch {
     type Output = ChainEpoch;
 

node/db/src/errors.rs

@@ -21,6 +21,12 @@ impl fmt::Display for Error {
     }
 }
 
+impl From<Error> for String {
+    fn from(e: Error) -> Self {
+        e.to_string()
+    }
+}
+
 impl From<rocksdb::Error> for Error {
     fn from(e: rocksdb::Error) -> Error {
         Error::Database(String::from(e))

vm/actor/Cargo.toml

@@ -21,3 +21,6 @@ ipld_blockstore = { path = "../../ipld/blockstore" }
 ipld_hamt = { path = "../../ipld/hamt" }
 forest_ipld = { path = "../../ipld" }
 message = { package = "forest_message", path = "../message" }
+
+[dev-dependencies]
+db = { path = "../../node/db" }

vm/actor/src/lib.rs

@@ -5,8 +5,10 @@
 extern crate lazy_static;
 
 mod builtin;
+mod util;
 
 pub use self::builtin::*;
+pub use self::util::*;
 pub use vm::{ActorID, ActorState, Serialized};
 
 use ipld_blockstore::BlockStore;

vm/actor/src/util/balance_table.rs

@@ -0,0 +1,132 @@
+// Copyright 2020 ChainSafe Systems
+// SPDX-License-Identifier: Apache-2.0, MIT
+
+use crate::HAMT_BIT_WIDTH;
+use address::Address;
+use cid::Cid;
+use ipld_blockstore::BlockStore;
+use ipld_hamt::{Error, Hamt};
+use num_traits::CheckedSub;
+use vm::TokenAmount;
+
+/// Balance table which handles getting and updating token balances specifically
+pub struct BalanceTable<'a, BS>(Hamt<'a, String, BS>);
+impl<'a, BS> BalanceTable<'a, BS>
+where
+    BS: BlockStore,
+{
+    /// Initializes a new empty balance table
+    pub fn new_empty(bs: &'a BS) -> Self {
+        Self(Hamt::new_with_bit_width(bs, HAMT_BIT_WIDTH))
+    }
+
+    /// Initializes a balance table from a root Cid
+    pub fn from_root(bs: &'a BS, cid: &Cid) -> Result<Self, Error> {
+        Ok(Self(Hamt::load_with_bit_width(cid, bs, HAMT_BIT_WIDTH)?))
+    }
+
+    /// Retrieve root from balance table
+    #[inline]
+    pub fn root(&mut self) -> Result<Cid, Error> {
+        self.0.flush()
+    }
+
+    /// Gets token amount for given address in balance table
+    #[inline]
+    pub fn get(&self, key: &Address) -> Result<TokenAmount, String> {
+        Ok(self
+            .0
+            .get(&key.hash_key())?
+            // TODO investigate whether it's worth it to cache root to give better error details
+            .ok_or("no key {} in map root")?)
+    }
+
+    /// Checks if a balance for an address exists
+    #[inline]
+    pub fn has(&self, key: &Address) -> Result<bool, Error> {
+        match self.0.get::<_, TokenAmount>(&key.hash_key())? {
+            Some(_) => Ok(true),
+            None => Ok(false),
+        }
+    }
+
+    /// Sets the balance for the address, overwriting previous value
+    #[inline]
+    pub fn set(&mut self, key: &Address, value: TokenAmount) -> Result<(), Error> {
+        self.0.set(key.hash_key(), value)
+    }
+
+    /// Adds token amount to previously initialized account.
+    pub fn add(&mut self, key: &Address, value: TokenAmount) -> Result<(), String> {
+        let prev = self.get(key)?;
+        Ok(self.0.set(key.hash_key(), prev + value)?)
+    }
+
+    /// Adds an amount to a balance. Creates entry if not exists
+    pub fn add_create(&mut self, key: &Address, value: TokenAmount) -> Result<(), String> {
+        let new_val = match self.0.get::<_, TokenAmount>(&key.hash_key())? {
+            Some(v) => v + value,
+            None => value,
+        };
+        Ok(self.0.set(key.hash_key(), new_val)?)
+    }
+
+    /// Subtracts up to the specified amount from a balance, without reducing the balance
+    /// below some minimum.
+    /// Returns the amount subtracted (always positive or zero).
+    pub fn subtract_with_minimum(
+        &mut self,
+        key: &Address,
+        req: &TokenAmount,
+        floor: &TokenAmount,
+    ) -> Result<TokenAmount, String> {
+        let prev = self.get(key)?;
+        let res = prev.checked_sub(req).unwrap_or_else(|| TokenAmount::new(0));
+        let new_val: TokenAmount = std::cmp::max(&res, floor).clone();
+
+        if prev > new_val {
+            // Subtraction needed, set new value and return change
+            self.0.set(key.hash_key(), new_val.clone())?;
+            Ok(prev - new_val)
+        } else {
+            // New value is same as previous, no change needed
+            Ok(TokenAmount::default())
+        }
+    }
+
+    /// Subtracts value from a balance, and errors if full amount was not substracted.
+    pub fn must_subtract(&mut self, key: &Address, req: &TokenAmount) -> Result<(), String> {
+        let sub_amt = self.subtract_with_minimum(key, req, &TokenAmount::new(0))?;
+        if &sub_amt != req {
+            return Err(format!(
+                "Couldn't subtract value from address {} (req: {}, available: {})",
+                key, req, sub_amt
+            ));
+        }
+
+        Ok(())
+    }
+
+    /// Removes an entry from the table, returning the prior value. The entry must have been previously initialized.
+    pub fn remove(&mut self, key: &Address) -> Result<TokenAmount, String> {
+        // Ensure entry exists and get previous value
+        let prev = self.get(key)?;
+
+        // Remove entry from table
+        self.0.delete(&key.hash_key())?;
+
+        Ok(prev)
+    }
+
+    /// Returns total balance held by this balance table
+    pub fn total(&self) -> Result<TokenAmount, String> {
+        let mut total = TokenAmount::default();
+
+        self.0.for_each(&mut |_, v| {
+            total += v;
+            Ok(())
+        })?;
+
+        Ok(total)
+    }
+}

vm/actor/src/util/mod.rs

@@ -0,0 +1,6 @@
+// Copyright 2020 ChainSafe Systems
+// SPDX-License-Identifier: Apache-2.0, MIT
+
+mod balance_table;
+
+pub use self::balance_table::BalanceTable;

vm/actor/tests/balance_table_test.rs

@@ -0,0 +1,109 @@
+// Copyright 2020 ChainSafe Systems
+// SPDX-License-Identifier: Apache-2.0, MIT
+
+use actor::BalanceTable;
+use address::Address;
+use vm::TokenAmount;
+
+// Ported test from specs-actors
+#[test]
+fn add_create() {
+    let addr = Address::new_id(100).unwrap();
+    let store = db::MemoryDB::default();
+    let mut bt = BalanceTable::new_empty(&store);
+
+    assert_eq!(bt.has(&addr), Ok(false));
+
+    bt.add_create(&addr, TokenAmount::new(10)).unwrap();
+    assert_eq!(bt.get(&addr), Ok(TokenAmount::new(10)));
+
+    bt.add_create(&addr, TokenAmount::new(20)).unwrap();
+    assert_eq!(bt.get(&addr), Ok(TokenAmount::new(30)));
+}
+
+// Ported test from specs-actors
+#[test]
+fn total() {
+    let addr1 = Address::new_id(100).unwrap();
+    let addr2 = Address::new_id(101).unwrap();
+    let store = db::MemoryDB::default();
+    let mut bt = BalanceTable::new_empty(&store);
+
+    assert_eq!(bt.total(), Ok(TokenAmount::new(0)));
+
+    struct TotalTestCase<'a> {
+        amount: u64,
+        addr: &'a Address,
+        total: u64,
+    }
+    let test_vectors = [
+        TotalTestCase {
+            amount: 10,
+            addr: &addr1,
+            total: 10,
+        },
+        TotalTestCase {
+            amount: 20,
+            addr: &addr1,
+            total: 30,
+        },
+        TotalTestCase {
+            amount: 40,
+            addr: &addr2,
+            total: 70,
+        },
+        TotalTestCase {
+            amount: 50,
+            addr: &addr2,
+            total: 120,
+        },
+    ];
+
+    for t in test_vectors.iter() {
+        bt.add_create(t.addr, TokenAmount::new(t.amount)).unwrap();
+
+        assert_eq!(bt.total(), Ok(TokenAmount::new(t.total)));
+    }
+}
+
+#[test]
+fn balance_subtracts() {
+    let addr = Address::new_id(100).unwrap();
+    let store = db::MemoryDB::default();
+    let mut bt = BalanceTable::new_empty(&store);
+
+    bt.set(&addr, TokenAmount::new(80)).unwrap();
+    assert_eq!(bt.get(&addr), Ok(TokenAmount::new(80)));
+    // Test subtracting past minimum only subtracts correct amount
+    assert_eq!(
+        bt.subtract_with_minimum(&addr, &TokenAmount::new(20), &TokenAmount::new(70)),
+        Ok(TokenAmount::new(10))
+    );
+    assert_eq!(bt.get(&addr), Ok(TokenAmount::new(70)));
+
+    // Test subtracting to limit
+    assert_eq!(
+        bt.subtract_with_minimum(&addr, &TokenAmount::new(10), &TokenAmount::new(60)),
+        Ok(TokenAmount::new(10))
+    );
+    assert_eq!(bt.get(&addr), Ok(TokenAmount::new(60)));
+
+    // Test must subtract success
+    bt.must_subtract(&addr, &TokenAmount::new(10)).unwrap();
+    assert_eq!(bt.get(&addr), Ok(TokenAmount::new(50)));
+
+    // Test subtracting more than available
+    assert!(bt.must_subtract(&addr, &TokenAmount::new(100)).is_err());
+}
+
+#[test]
+fn remove() {
+    let addr = Address::new_id(100).unwrap();
+    let store = db::MemoryDB::default();
+    let mut bt = BalanceTable::new_empty(&store);
+
+    bt.set(&addr, TokenAmount::new(1)).unwrap();
+    assert_eq!(bt.get(&addr), Ok(TokenAmount::new(1)));
+    bt.remove(&addr).unwrap();
+    assert!(bt.get(&addr).is_err());
+}